The present invention pertains to debris-free fastener collations. More particularly, the present invention pertains to an apparatus for making a debris-free collated nail strip formed with a plastic material for use in a fastener driving tool.
Fast-acting fastener driving tools are in widespread use in the construction industry and used in industries ranging from pre-fabricated housing construction to luxury residential, commercial and industrial construction.
The nails that are used in these tools are assembled in strips that are inserted into a magazine. There are two principal nail strip or nail collation formations—paper tape and plastic. As the name suggests, paper tape collations maintain the nails in a strip by using a strip of tape that is adhered to one or both sides of the arranged nails. Plastic collations use a formed or pre-formed collar-type element to secure the fasteners to one another and parallel in the strip form.
Paper tape has certain advantages, one of which is ease of manufacture. In addition, paper tape collations, which use a glue or adhesive to adhere the tape to the fasteners, tend to be quite rigid, but sufficiently easy to separate one fastener from an adjacent fastener, as when the fastener is driven from the tool into a substrate. While rigidity on the one hand is good for the collation in that it reduces the opportunity for strip corrugation, on the other hand, it tends to require additional force to separate the fastener from the strip. Moreover, paper tape collations also produce a significant amount of debris when the fastener is separated from the strip. This debris can cause increased tool maintenance as well as jamming and increased down-time for tool repair.
Plastic collations use a collar that is molded to or fit around the shank of the fasteners. The collars are connected by bridges that break or separate to permit the fastener to be separated from the strip. One drawback to commonly available plastic collations is that the collation, although molded around the fastener, is nevertheless only superficially affixed to the fastener. That is, although the fastener is supported within and by the collation, the fastener can be rotated within the collar. It may not be loosely held, but can nonetheless be rotated. This has two ramifications.
First, because the fasteners are loosely supported, the collation can be overly flexible. This can result in increased corrugation of the strip in the tool magazine. Second, because the plastic is only loosely affixed to the fastener, it has been observed the plastic collars and bridges fracture as the fastener is driven into the substrate. This has been shown to result in the generation of debris, and in certain instances substantial amounts of debris. At times, it has also been found that the collars collect under the fastener head, thus preventing the fastener from being driven fully into the substrate. This may thus require a user to then drive, by hand, e.g., with a hammer, the fastener the remainder of the way into the substrate. Another drawback to the known plastic collations was that because the collation material was quite brittle, the downstream collation fractured, causing fasteners to become off-centered in the tool, which resulted in tool jams and misfires.
In an effort to eliminate the drawbacks associated with the generation of debris and the accumulation of material under the fastener head, and off-centered driven fasteners, a debris-free fastener was developed that uses an adhesive-modified chemistry for the plastic collation material in conjunction with preheating the fasteners prior to application (molding) of the collation.
It was found that the improved, debris-free collation generated significantly less debris and that the plastic collation material adhered well to the fastener shank. As a result, the plastic material entered the substrate as the fastener was driven from the strip into the substrate. Such a fastener collation is disclosed in Shelton, U.S. patent application Ser. No. 11/383,032, filed May 12, 2006, Shelton, U.S. patent application Ser. No. 11/734,684, filed Apr. 12, 2007, and Heskel, U.S. patent application Ser. No. 11/935,541, filed Nov. 6, 2007, all of which are commonly assigned with the present application and are incorporated herein by reference.
While the above-noted fastener collations overcame many of the drawbacks in prior fastener collations, they were found to be very difficult to manufacture. Using known manufacturing devices and techniques resulted in too much flow of the collation material and thus mis-formed collations, sticking of the collation material to the forming molds, and other manufacturing obstacles.
Accordingly, there is a need for an apparatus for forming a plastic collation system for strip-formed fasteners. Desirably, such an apparatus provides a high quality collation formed on the fasteners. More desirably, such an apparatus uses portions of known extruders to apply adhesive-modified materials for the plastic collation. More desirably still, such a collation forming apparatus provides a high speed process with little to no waste or rejection of product. Most desirably, such a device is used to form a plastic collation formulated from an adhesive polymer such as a polyolefin, such that when the fastener is driven from a driving tool, the collar portion remains adhered to the fastener so that the collar portion penetrates the substrate with the fastener.